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Convert 'pedal assist only' to 'thumb throttle'. Is it possible?

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    Convert 'pedal assist only' to 'thumb throttle'. Is it possible?

    Dear Everyone,

    Is it possible to use a thumb throttle on an ebike that is originally has only pedal assist mode? I found this: . The system is 36V and I think the torque sensor is faulty (it's something like this: The sensor's connector is 3 pin, like the thumb throttle, visually they look the same to me. What would happen if I just plug in this thumb throttle? Can I damage anything? The torque sensor is way too expensive (almost $200), that's why I'm thinking about this thumb throttle.

    Hi gyorfitam,
    And welcome to the forum!

    A hall sensor throttle outputs 1vdc to 4 vdc in a linear fashion. Low to high.
    A PAS sensor, typical passive magnetic ring outputs a kind of 5 vdc digital pulse.

    These two are absolutely different.

    Now a true torque sensor will have a different output depending on it's manufacturer... see below, and would perhaps need some serious modification of the throttle output. If at all possible. See Hall Sensor Throttle Operation...

    Force Signal

    The torque signal from these sensors is usually a straightforward voltage in the 0-5V signal range. The table below shows the resting voltage with no torque on the crank and the voltage you get with maximum torque for various sensors that we have offered. Notice how some sensors start at 2.5V and then decrease in voltage as torque is applied, others increase in voltage, and none have the same overall scaling for Nm / volt.
    Sensor Type Offset Voltage Full Torque Voltage
    THUN / NCTE 2.5 V 0.5V
    TDCM 2.5V 3.3V
    SEMPU 1.5V 4.0V
    Cycle Stoker 1-2V 4.5V
    Taken from this article READ ME!

    Would it damage your controller to try? They all use 5vdc regulated supply. A hall sensor will draw ~6.5 mA. Your call. But I'd sure want to verify my existing torque sensor output first to see if the swap would be even close. A long shot IMHO.

    Any possibility that the controller has a throttle input that's just not being used? I'd sure take a look...

    See my completed Magic Pie V5 rear hub motor E-Bike build HERE.


      The day will come when all production bikes will be looking for such a mod. I have a BBSHD and now look for a way for the throttle to only work when pedaling. Totally stupid, but then I can call it a variable mode selector. Never found a way to do this with programming. Anybody else?


        xcnick - We figured out how to get throttle only operation that does the same thing as removing the "gray" pedal cadence sensor wire in this thread:

        It just makes the controller completely ignore the pedal sensor so now you can pedal and throttle at the same time but PAS no longer works - very fun mode of operation but admittedly it can fatigue your wrist since you always need to have a hand on the throttle to have power

        I [and some others on ES] have got circuits that go in the controller to make them support both modes


        • Retrorockit
          Retrorockit commented
          Editing a comment
          I would go to twist throttle for full time throttling.

        • AZguy
          AZguy commented
          Editing a comment
          Couldn't agree more but then again coming from the moto world I don't like thumb throttles to begin with!

          I would still get wrist fatigue when running in throttle only mode but have since added the little circuit to make it work seamlessly in both modes and so use PAS whenever cruising and for a lot of conditions where constant power is useful and the throttle for varying conditions and for quick adjustments or boosts

        In this case I think it's worth to share the whole story.
        So I bought a used Giant Escape 2 electric bike on eBay. It worked fine for a shorter time. I had 2 batteries, I sent one of them to someone who replaced the cells so I had 2 proper batteries. Within few weeks it started to do 2 strange things: 1. It doesn't help me when it should be like 50% of the time, 2. When the motor is not on (either it doesn't turn on to help me or I turn off the whole system) it has a serious drag, it feels like I have to pedal a 100kg bike, so it's definitely not a pleasant experience. I went to few places with it (Giant Service included), but no one could figure out what's causing this issue. I have a feeling that the torque sensor is the problem. So I thought that a throttle could be a simple solution.
        the problems are: 1. I already spent a fortune on this bike (mechanically it's perfect, almost everything is new, I had to replace quite few things) but it's still useless because of the electric parts, so selling is not really an option, 2. I'm absolutely dumb for electronics, so I can only do the simplest things, 3. It's impossible to gather any information about the bike's specifications. I have a service guide pdf but it doesn't seem too useful (no specs about the electric parts).
        Any suggestions? Is it worth to buy a whole kit with a new motor and use the batteries I have?


        • xcnick
          xcnick commented
          Editing a comment
          My sympathies. Maybe start a new thread with some pics.

        Without any PAS I use this just to hold it open. Instead of using throttle over a log I give a good pedal stroke over the log. When it gets technical I prefer to use my wrist on the infinitely variable mode controller. Funny how much better this assists my pedaling than production bikes computer estimates of what I what.

        Click image for larger version

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        I just have one controller that worked on 0 well and I thought maybe I was missing something with the other one.


          Yeah - I'd try that setup I posted in the thread with the settings. Everyone I know with moto background loves it. The monsoon finally gave some little breaks so I was able to go and get a bunch of miles on the new cassette/ring/chain setup - it's awesome!!! Ran it all weekend with the throttle controlled assist and used every gear.

          The three level throttle control works really well. 99% of the time I just leave it in level one with 750W max which gives great throttle feel and limits that "medical condition" I have in my wrist that tends to flog throttles ;-}

          I climbed some wickedly steep stuff and on one even needed 1000W (level two) which was adequate and bumped it to 1500W (level three) just so I wasn't just full throttle for the climb.

          Where'd you get that throttle lock? I'm ready to try one...



            Good for texting and riding as well.

            I have that medical condition. You know one more blip and it will trigger the BMS and you do it anyways.


              Ok Yes You can do this.I have a Juiced Bike I bought from a pawn show.I had no idea it was valued at $2500 but the pawn shop and myself both knew it was going to be hard to figure this out since the bike was a torque sensorwhich is different form of activating the rear tire.So I went ahead and tested the torque to find out it was malfunctioning.The Store Juiced biked out of cali flipped out on me when I called them,.They claimed these bikes can not be sold under and circumstance to a third party and that I was not allowed to own this bike without proving who the previous ower was.I could not get that information because the pawn shop has a clause that does not allow them to identify a person who sells an item unless the item pawned turned out to be stolen.SO they refused to help me and refused to sell me parts.The lady seemed like a phycopath and a real one at that.I reminded her we both lived in America and that we are still free.She said you will never get these parts because your not allowed to buy this bike without first contacting us.I told her to F O called her a b and looked to see if they had a web site for parts.Sure enough they did and sure enough noone asked me to prove im the owner of the bike they just took my credit card and shipped out the parts.Because of this complete insanity on JUICED BIKES I was peaked to crack the code of what they didn't want me to know so I took apart the torque and stripped the wires down and started to test wire against wire and 99% of the tests failed.So here is the secret.In order for you to use the bike without pedaling,You have to re produce a pulse to trigger the bike into thinking your pedaling.The way you do that is when you strip the plastic off the ends of the wire,My torque sensor had three wires in one direction and three wires branching into another direction.SO I figured combining different random touches to the wires would activate it.So I started touching white on red and blue on yellow and so on so the three wires on one branch id touch to the three on the other branch and it kicked off the rear tire for a second.Remember to have the power on.SO it turned out that on a 2018 Juiced Cross Current $2500 bike will allow you to activate the rear tire but instead of twisting the wires together so that it stays on,It wont do it that way.You have to keep touching the two wires black and yellow to each other and the pulse of them two wires touching each other keeps the bike motor activated.So the real question is how can we re produce this pulse in a device that allows us to keep the hub powered.My idea is to make it so as a device will allow you to spin something that forced the two wires to keep touching each other each time they move one revaloution for example and this will solve all of our problems.The company does not want us to figure this out because them torque pressure plates they sell cost $200 to replace.My point is if we spend $2500 to buy a bike it darn well better allow the buyer to not pedal when that person chooses.ANd Juiced Bikes from California lost there minds.A bit retarded and the manager is banging the women there because they all swallowed and repeated the same lies.
              By touching the two wires and then remove the wire then retouch it creates a pulse to keep the tire moving.How do we reproduce this/


              • paxtana
                paxtana commented
                Editing a comment
                Would love to hear their side of the story regarding all that, but in any case if you are that much into modding it might as well just replace the controller with one that accepts throttle input


              Interesting read!

              I am curious about the complete opposite. Because of retarded regulations where I live I am wondering if it is possible to convert my 5000W Ebike from throttle to pedal assist.

              It's this even possible or just insane? :)


                Please guys help... from PAS to throttle is it possible


                  Depends on the equipment but for the most part you would need to change the controller which would also entail rewiring significant other portions of the bike


                    On the TSDZ2 you need to change the controller inside the motor to get the extra wiring needed. Like Paxtana said then rewire the bike controls.


                      Can I add either a thumb or twist grip throttle to my bike
                      I have a Halfords carrera crossfire pedal assist bike
                      With a Sun tour Motor in the back wheel a single controller
                      I want to add maybe a boost button or throttle to help me with the hills
                      As I have arthritis in both knees
                      I see you can buy loads of throttled but they might not work
                      Can you advise
                      Last edited by alanya2010; 10-17-2021, 11:40 PM.


                        It should say Crossfire & Suntour